1. Field of the Invention
This invention relates to static humidifiers in general and more particularly to a humidifier system which uses the heat of waste gas from a forced air furnace to produce steam.
2. Description of the Prior Art
It is often desirable to provide and maintain a predetermined humidity level by means of a humidifier incorporated into the forced air heating system. Static water pan humidifiers have failed to generate sufficient humidity for dry weather regions, while power driven humidifiers have usually required an additional electrical power source. For economy and efficiency, it is highly desirable to utilize the existing furnace components without extensive or expensive modification. It is known, for example, that one can use the heat of waste combustion gas from a gas or oil furnace to produce steam in a humidifier system. Reed U.S. Pat. No. 4,054,122 discloses such a system. However, systems of this type do not efficiently utilize the steam generation capacity of the waste combustion gas or the steam generated thereby. The Reed humidifier system, for example, employs a coil formed from plain tubing which is disposed in the waste gas exhaust duct of a gas furnace and in which steam is generated. Such a conventional coil does not promote enhanced heat transfer from the combustion gas to the water and thus requires that a substantial length of the tubing be maintained in the exhaust duct in order to achieve the required steam generation for adequate humidity in the living space. Efficient heat transfer requires that the coil tube be surrounded by the hottest gas which has been found in different locations of the flue pipe depending on the shape and angle of the flue pipe.
In addition, the prior humidifiers of this type have typically utilized a drip chamber positioned outside the ductwork of the furnace system, and hence apparently at about ambient temperature, for separating unvaporized water and sediment from the steam for use in regulating the humidity. The unvaporized water and sediment are collected in a lower portion of the separation zone whereas the steam passes through the upper portion of the zone. Being substantially cooler than the steam, the separation zone would tend to cool the steam passing through it and to promote condensation of the steam in the zone. The humidifier system of the present invention overcomes the drawbacks and deficiencies of these prior systems to create the desired humidity in an efficient and economical manner by enhancing the efficiency of the transfer of heat from the waste combustion gas from a gas or oil furnace to the water and of the transfer of steam to the air flow system of the furnace as well as transfer of heat from the water vapor to the air.